The Elm Reader is a new tool designed to provide a beautiful interactive environment for reading and exploring code written in the Elm programming language. We hope you'll use the Elm Reader to debug your own projects, to familiarize yourself with code written by others, and to share rich visual demonstrations of your algorithms with the world.
Reading code is a very different experience from writing it, and we've optimized the design of the Elm Reader to make understanding an unfamiliar codebase as comfortable and efficient as possible. In addition to static code navigation features like type inspection and jump-to-definition, the Elm Reader is based on a powerful runtime tracing system which reveals the values flowing through every expression in your program. By leveraging Elm's purely functional design, we can provide a nonlinear debugger without the concept of time, allowing you to freely explore your program's execution either forwards or backwards.
The Elm Reader is designed to complement, not compete with, the Elm Reactor; while the Reactor shows the high-level changes to your program's state over time, the Elm Reader will allow you to navigate deep into your program and inspect the behavior of individual expressions. If the Elm Reactor shows what is happening, then the Elm Reader helps illuminate why and how your program behaves the way it does.
The Elm Reader is being developed as an unofficial extension to the Elm compiler, and is currently in an extremely early stage of development. Questions and contributions are welcome! Please contact William Brandon or Wilson Berkow to learn more.